Tous les combattants
 | Oļegs Jemeļjanovs | 0-2-0 REC | #6176 |  |
 | Oleksandr Moisa | 2-1-0 REC | #1211 |  |
 | Oleksii Polischuck | 4-4-0 REC | #1799 | |
 | Olena Kolesnyk | 4-4-0 REC | #3375 | |
 | Olendet Apouassa Romeo | 0-1-0 REC | #5767 |  |
 | Olga Rubin | 4-3-0 REC | #2234 |  |
 | Oli Thompson | 0-2-0 UFC | #5219 |  |
 | Oliver Enkamp | 0-2-0 UFC | #3812 |  |
 | Oliver Tero | 1-1-0 REC | #2093 | |
 | Olivia Hendrickson | 1-0-0 REC | #5087 |  |
 | Olivia Parker | 0-1-0 REC | #5292 | |
 | Olivier Aubin-Mercier | 7-5-0 UFC | #186 |  |
 | Olivier Fleurmon | 1-0-0 REC | #2148 |  |
 | Olivier Murad | 1-0-0 REC | #5587 |  |
 | Olli Santalahti | 2-3-0 REC | #3561 |  |
 | Ollie Sarwa | 5-1-0 REC | #427 | |
 | Ollie Schmid | 0-1-0 UFC | #3148 |  |
 | Olutobi Kalejaiye | 1-1-0 REC | #1652 |  |
 | Oluwale Bamgbose | 1-4-0 UFC | #3628 | |
 | Olzhas Moldagaliev | #8104 |  | |
 | Omar Amasha | #7789 |  | |
 | Omar El Bily | 0-1-0 REC | #6116 |  |
 | Omar El Dafrawy | 6-1-0 REC | #331 | |
 | Omar Hussein | 1-2-0 REC | #625 |  |
 | Omar Morales | 3-4-0 UFC | #2554 |  |